1. Field of the Invention
The present invention relates to microwave connectors used to connect coaxial conductors to microwave components, In particular, the present invention relates to an inner conductor for a coaxial microwave connector designed to provide an axially resilient connection with microwave devices at high microwave frequencies.
2. Description of the Related Art
FIG. 1A shows a microwave coaxial transmission line 10 which requires two contacts for connection with a microwave device. One contact is an outer conductor 20 and the other contact is an inner conductor 30. Both of these conductors form an axial connection with a microwave device. That is, to make a pressure connection with the microwave device, pressure is provided in the direction of the central axis 40 of the inner 30 and outer 20 conductors.
In an axial connection, only one of the contacts can be firm, while the other contact must be resilient as depicted in FIG. 1B. FIG. 1B is a side view of outer conductors 20 and inner conductors 30 of two microwave coaxial transmission lines that are to be connected, A firm connection 50 exists between the outer conductors 20 while a resilient connection 60 exists between the inner conductors 30. The resilient connection 60 is necessary to absorb the variations in the relationship between the outer 20 and inner 30 conductors. Additionally, the resilient connection 60 must be maintained at a constant impedance. To maintain a constant impedance, a requisite amount of axial pressure 70 must be provided by the inner conductors 30.
The requisite amount of axial pressure 70 is difficult to maintain at microwave frequencies because, as the frequency of the operation of a microwave device increases, the parts in a microwave coaxial line must be very small. The diameter of the coaxial line must be reduced as the frequency of the operation increases. Thus, as microwave devices move to higher frequencies, their parts must necessarily get smaller, and the designs of the larger, low-frequency connectors become infeasible. When connector sizes are reduced, the requisite axial pressure needed to maintain a stable connection becomes more difficult to provide.
Conventional inner conductors of coaxial connectors have been used as shown in prior art FIGS. 2A-2C to provide an axially resilient coaxial connection between a conventional inner conductor and a microwave device at microwave frequencies. However, as described below, the parts used in these conventional inner conductors at microwave frequencies are too small to provide the necessary axial pressure to maintain the requisite pressure.
Prior art FIG. 2A shows a side view of a first conventional inner conductor 80 for a coaxial connector known as a GPC-7 connector. A first portion 100 of the first conventional inner conductor 80 has been removed in the side view so that a first resilient contact 110 located within a first bore 90 through the first conventional inner conductor 80 may be viewed. The first conventional inner conductor 80 has a metal barrel 111 with barrel slots 112 extending along the metal barrel 111. The first conventional inner conductor 80 has lips 120 to hold the metal barrel 111. In operation, the barrel slots 112 expand into the first bore 90 to make electrical contact when inserted therein. Such an inner conductor configuration, however, becomes impractical to manufacture for small sizes required at high microwave frequencies.
Prior art FIG. 2B shows a second conventional inner conductor 121 of a conventional coaxial connector. A second portion 130 of the second conventional inner conductor 121 has been removed to view a second resilient contact 140 located within a second bore 150 through the second conventional inner conductor 121. The second resilient contact 140 is composed of a spring 160 connected to a contact plunger 170. The spring 160 maintains contact against the contact plunger 170 to provide axial pressure 180 and thereby maintain a constant impedance against a microwave device (not shown). Resiliency is provided by the spring 160 that provides axial pressure 180 and maintains a constant impedance. The problem with the second conventional inner conductor 121 is that, at microwave frequencies, the spring 160 must be very small and becomes difficult to manufacture, and if such a small spring is available, axial pressure 180 provided by the small spring 160 is not sufficient to maintain the requisite pressure.
Prior art FIG. 2C shows a third conventional inner conductor 190. A third portion 200 of the third conventional inner conductor 190 has been removed to view a third resilient contact 210 located within a third bore 220 through the third conventional inner conductor 190. The third resilient contact 210 is a thin wall bellow which functions as a spring to provide axial pressure 240 to maintain a constant impedance with a microwave device. However, manufacturing such thin walled bellows becomes impractical and expensive when frequencies are significantly increased.
It is, therefore, desirable to have an inner conductor for a high frequency microwave coaxial connector that maintains sufficient axial pressure for a constant impedance while providing an axially resilient coaxial connection with a microwave device. Since operation of the microwave device is at microwave frequencies, the connector must be able to provide the axial pressure and constant impedance with very small parts.